曙红亚甲基蓝分光光度法测定水中阳离子表面活性剂

采用分光光度法测定水样中阳离子表面活性剂的含量。在弱酸性的HCl-NaAc缓冲介质中,阳离子表面活性剂十六烷基溴化吡啶(CPB)以及十六烷基三甲基溴化铵(CTAB)能与曙红亚甲基蓝反应,形成离子缔合物,后者的最大吸收波长分别为660 nm和658 nm,且阳离子表面活性剂的浓度与溶液的显色程度呈良好线性关系。在最大吸收波长处,CPB和CTAB的浓度分别在0~2.10×10-5mol/L和0~1.98×10-5mol/L范围内遵守比尔定律,表观摩尔吸光系数分别为1.79×104L/(mol.cm)和1.38×104L/(mol.cm),检出限分别为8.27×10-7mol/L和9.88×10-7mol/L,平均回收率为99.5%~102.6%。方法具有较高的灵敏度和良好的选择性,可用于水样中阳离子表面活性剂的测定。

Spectrophotometric method for determination content of cationic surfactants with eosin methylene blue

A sensitive spectrophotometric method is developed for determination of content of cationic surfactants (CSs) in water samples.In weak acidic HCl-NaAc buffer medium,some cationic surfactants reacts:cetylpyridinium bromide (CPB) and cetyltrimethylammonium bromide(CTAB) with eosin methylene blue (EMB) to form an ion-association complex,and the maximum absorption wavelength is 660 nm and 658 nm respectively.At such maximum absorption wavelength,the color intensity shows good linearity with the concentration of the CS.Within the range 0～2.10× 10-5mol/L and 0～1.98×10-5mol/L of CPB and CTAB respectively,the relationship between the color intensity and concentration of the CSs follows Beer's Law.The apparent molar absorptivity ε is 1.79×104 L/(mol·cm) and 1.38×104 L/(mol·cm) respectively and the detection limit is 8.27×10-7 mol/L and 9.88×10-7 mol/L respectively.Average recovery is 99.5%~102.6%.The method has high sensitivity and fairly good selectivity.This method can be applied for the determination of cationic surfactants in water samples.